1. Field of the Invention
This invention relates to hydrotreating catalysts and a process of preparing the same. More particularly, the invention is directed to the provision of such a hydrotreating catalyst which is useful for the hydrotreatment of hydrocarbon oils and heavy hydrocarbon oils inter alia containing substantial amounts of sulfur, nitrogen and metallic compounds.
2. Prior Art
Hydrogenation or hydrotreating catalysts introduced to date typically comprise catalyst components selected from Group VIB and Group VIII metals deposited on alumina carriers. Many attempts have been made to improve their catalytic activity and service life. To this end, for example, it is proposed in Japanese Patent Publication No. 56-35893 to use a pseudo-boehmite having a crystal diameter of 40-80.ANG. as an alumina hydrate precursor for a porous alumina carrier. Japanese Patent Laid-Open Publication No. 56-105754 discloses the use of a catalyst carrier comprising boehmite admixed with an organic polymer selected from the group of PVA, polyvinylpyrrolidone, hydroxypropyl cellulose, methylcellulose or mixtures thereof, the boehmite admixture being molded and calcined. U.S. Pat. No. 4,048,060 proposes to use an alumina carrier having a specific pore size distribution. Japanese Patent Laid-Open Publication No. 52-59094 teaches precipitating an alumina hydrate with an aqueous solution containing a water-soluble aliphatic polycarboxylic acid such as gluconic acid having 4-22 carbon atoms.
However, the prior art hydrotreating catalysts have still much to be desired in terms of catalytic activity and service life when used for instance in the hydrodesulfurization of hydrocarbon oils, particularly heavy hydrocarbon oils such as residual oils.